First report on the molecular characterization and phylogenetic analysis of meq oncogene from virulent serotype-1 Marek's disease virus in laying hen flocks and broiler breeders in Algeria

Abstract

Marek's disease (MD) is a highly contagious viral infection in poultry, caused by Gallid alphaherpesvirus 2 (GaHV-2), better known as serotype 1 of Marek’s disease virus (MDV-1). It is one of the most concerning diseases in the poultry industry due to its significant economic impact. The disease mainly affects chickens, although other avian species can also be affected. The objective of this study was to examine the occurrence of Marek's disease virus (MDV) in fourteen poultry farms in Algeria through autopsy, histopathological analysis and molecular characterization of Marek's disease virus. This study represents one of the first investigations combining macroscopic, histopathological, and molecular analyses to assess the prevalence and genetic diversity of Marek's disease virus in Algerian poultry farms. A survey to assess the current occurrence of Marek's disease in poultry farms in Algeria was conducted from June to December 2024. Tissue samples were collected from 70 chickens, including 35 from broiler breeder farms and 35 from layer farms. Macroscopic and histopathological examinations were performed. Macroscopic pathological alterations, such as hepatomegaly, splenomegaly, renal hypertrophy, and sciatic nerve enlargement with follicular atresia and lymphomatous infiltration, were observed. Histopathological analyses revealed diffuse and multifocal whitish infiltration of the spleen, neoplastic infiltration of the liver, intrafollicular lymphoid infiltration in the bursa of Fabricius, and infiltration in the sciatic nerves. The molecular characterization of MDV through PCR amplification and sequencing of the meq gene provides novel insights into the circulating strains in Algeria. The samples were screened by PCR amplification of the meq gene. Additionally, we sequenced the meq gene from five samples per flock, and a phylogenetic tree was constructed using the deduced amino acid sequences of the meq gene. This study is the first to identify and classify MDV strains in Algerian broiler breeder and laying hen farms, revealing the presence of very virulent (vv) MDV pathotypes. Marek's disease remains a major veterinary and economic challenge in the poultry industry, requiring ongoing research to better understand its mechanisms, genetic variations, and control methods.